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Floor insulation advice

What is the build up of a floor to meet with the Building Regulations for thermal insulation?


The Building Regulations require that, in some circumstances, the floor should contain insulation to achieve the heat loss estimates for the room and/or house as a whole. This has led to an increased use of heated concrete floors or screeds.

A concrete floor can be termed ‘cold’, i.e. concrete placed below the insulation or ‘warm’ i.e. the concrete above the insulation.

A ‘Cold’ construction build-up would be:

- Sub-base
- Polythene membrane /DPM
- Concrete slab (minimum 100mm thick)
- DPM layer
- Insulation
- Floor finish

Floor finishes include; Floating timber floors; Floating sand/cement screed (can be heated) of minimum 75mm thickness (65mm for domestic); Floating concrete slab, minimum 100mm thick (can be heated) and sheet flooring, e.g. carpet, tiles etc. Any of these may require a polythene membrane below.

Warm construction build-up would be:

- Sand blinded sub-base
- Polythene membrane (DPM)
- Insulation (rigid board type)
- Concrete slab min. 100mm thick (can be heated)
- Levelling screed (as required: self levelling compound, sand/cement screed etc)
- Flooring, e.g. carpet, tiles etc.

Acknowledgement: The Concrete Society

Other references:BS 8204 ´Screeds bases and insitu floorings´
HMSO Building Regulations Part L

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Screeds with underfloor heating